NaNbO3 (NN) is a widely studied antiferroelectric ceramics. However, NN ceramics always exhibit a square P-E loop with larger Pr, originating form an irreversible antiferroelectric-ferroelectric (AFE-FE) phase transition under an applied electric field, which limits further development. Here, a novel lead-free relaxor ferroelectric ceramic, (1-x)NaNbO3-x(0.5Bi0.5Na0.5TiO3-0.5Ba0.3Sr0.7TiO3) [(1-x)NN-xBNBST, x = 0, 0.10, 0.15, 0.20, 0.25, 0.30], was designed and prepared via a local random field relaxation strategy. Dielectric testing shows that the addition of BNBST significantly improved the relaxor behavior of the NN, which is effective for enhancing the Wrec and ƞ of NN-based ceramics. When x = 0.2, the ceramic obtains a high recoverable energy storage density (Wrec = 2.024 J/cm3) and energy storage efficiency (ƞ = 63 %) at a low electric field of 130 kV/cm. Meanwhile, the polarization-electric field hysteresis loops and charge-discharge results of the sample with x = 0.2 at different temperatures and frequencies show that it is a prospective material for pulsed energy storage capacitors.

The 0.5Bi0.5Na0.5TiO3-0.5Ba0.3Sr0.7TiO3 (BNBST) ceramic is a relatively good relaxation component with tripartite phase and tetragonal phase coexisting at room temperature. Tripartite R3c is a polar phase, which can transform to long range ordered ferroelectric structures under the action of an applied electric field, exhibiting large remnant polarization (Pr), which limits its application in energy storage. In this work, we have designed and fabricated the NaNbO3 (NN) modified Bi0.5Na0.5TiO3-Ba0.3Sr0.7TiO3 (1-x)BNBST-xNN relaxor ferroelectrics. By increasing the NN amount, the phase composition is regulated to induce the transformation of the polar phase R3c to the weakly polar phase P4bm, leading to a smaller Pr. The ferroelectric test results show that the ceramic sample with x = 0.1 achieves a high effective energy storage density (Wrec = 2.58 J/cm3) and energy storage efficiency (ƞ = 91 %) at 140 kV/cm.